Pluripotent cells provide an important opportunity for treating blindness. The long-term objective of this work is to heal the damaged retina using cell replacement therapies. Can retinal cells generated in culture properly differentiate into rods and rescue vision in the damaged eye? When is the best time to introduce cells into the damaged eye? This proposal addresses these questions using an innovative approach based on a new technique for reprogramming pluripotent to retinal cells and a novel animal model in which rod photoreceptors can be specifically, yet reversibly, ablated. Induced retinal progenitor cells are similar to endogenous retinal progenitors as they differentiate into all retinal cell types and even form functional eyes. In this proposal, these cells are implanted into the degenerated retina in order to determine if they survive, differentiate normally and repair functional vision. The optimal time for introducing the cells will also be determined. The aims are: Aim 1. Determine if induced retinal progenitor cells can restore visual function to a degenerating retina. Aim 2. Determine if biasing retinal progenitors to a photoreceptor lineage is required for efficient integration and functional repair. In Aim 1, induced retinal progenitor cells will be injected into the retina of transgenic Xenopus laevis, which lack rod photoreceptors. Immunohistochemistry will be used to determine if the injected cells form normal retinal cell types. A vision-based, behavioral assay will then be used to determine if the injected cells can repair the vision of the animals. In Aim 2, induced retinal progenitor cells will be used to identify the combination of extrinsic factors sufficient to preferentially generate rod photoreceptors. Rod-biased cells will then be microinjected into the photoreceptor-ablated retina at progressively later degenerative stages to determine when introduction of cells is most efficient, and if they more efficiently integrate into and functionally repair a degenerated retina than non-biased cells. The goals of this proposal directly address program objectives of the National Eye Institute, including Continued development of animal models... and to Further develop and critically evaluate therapies involving gene delivery, growth factors and transplantation for the treatment of retinal disease. This work provides a new and innovative approaches for generating induced retinal progenitor cells, will determine if these cells can be used to repair vision, and determine the optimal stage at which to introduce the cells. PUBLIC HEALTH RELEVANCE: Replacing lost or unhealthy retinal cells with functioning cells holds great promise for those suffering from blindness resulting from eye damage or disease, but the timing and conditions under which donor cells can repair vision must be determined. This project uses a simple animal model to identify the best time and optimal conditions required for donor retinal cells to survive, integrate into and ultimately repair the damaged retina.